Liquid dispensing valves of the type associated with the present invention generally provide for the selective flow of fluid, such as liquid with or without process air, through a valve body and then out of a nozzle orifice or liquid outlet. The process air may impart some characteristic to the liquid discharging from the nozzle orifice, such as swirling or otherwise moving a liquid filament, or atomizing the liquid as it is discharged. Control of the flow through the nozzle orifice is typically effected by reciprocating a valve member along a stroke length. The valve member ordinarily seats against a valve seat member which includes the nozzle orifice. Movement of the valve member away from the valve seat permits liquid to flow out through the orifice at a rate commensurate with the gap between the valve and the valve seat. Movement of the valve member against the valve seat prevents liquid flow through the nozzle orifice.
Various manners of accurately controlling flow of liquid through the nozzle orifice have been proposed in the past and are in practice today. For example, the size of the nozzle orifice itself may be changed by changing from one nozzle to another. However, nozzle changes are time consuming and require increased inventory of parts. Other methods involve changing the stroke length of the valve member so as to change the gap between the valve member and the valve seat when the valve member is in the open position. In the past, such stroke length adjustment mechanisms have had various drawbacks, for example, related to complexity of use and design, and repeatability of proper adjustments.
The fluid fittings used in typical liquid dispensing valves often use threads for connecting the fittings to the valve body. Unfortunately, threading a fluid fitting into place can result in inconsistent seal compression from one valve to another and this can result in leakage. Also, threaded fittings may be prone to the formation of cavities in which liquid stagnation may occur and this can be a problem especially in applications requiring aseptic conditions. Finally, threaded fittings may not be as easily modified to connect, for example, to a wide variety of push-on type flexible tubing, and may not be easily cleaned as may be necessary for certain applications, including aseptic applications.
For at least the reasons set forth above, it would be desirable to provide a liquid dispensing valve in which the stroke length is easily calibrated and set, and which provides improved fluid connections overcoming the drawbacks associated with the prior art.